jason's education thread

[Charlief1]

Things don't always go like you plan Jason. I'll be at work until 5 tomorrow and have to work till 12 on Saturday. TTYS my friend. Talked to Gary today and Ray called me back but we'll chat soon.

[good2win22]

Made a few pulls in 3rd gear last Sunday evening.  O2's were in the 770's above 100 mph.


To recap:  adjusted fuel pressure to a tad under 43 psi.  Blm's at idle 132. O2's at 780ish, hot, in gear


Checked an ass load of electrical wires for voltage loss. Added grounds at intake to firewall, back of alternator to fender, and one at the tank to the trunk floor.


Replaced alternator with a junkyard score out of a buick roadmaster.


Cleaned all elctrical connections and fuse block with Deoxit D5(man is that stuff hard to find)


Swapped ECM's with my spare to include the power logger.


Removed all bulbs and head lights, cleaned all sockets


Adjusted alky control  to 6 on the dial instead of 7.


Now just need to get to the track to see what's happening at low gear

[good2win22]

Sitting at work twiddling my thumbs....  Playing with compression ratio calculator on the computer.  What are some dimensions of head gasket thickness you guys have used? Any problems?  Brands?  I believe stock had a compressed thickness of .060.  Cometic has the MLS available in several thicknesses.  Not certian of the TRW piston cc's either.  I have found several conflicting numbers for piston cc's for their .030 over piston.

[larrym]

I plan on trying RJC gaskets with the motor I have on the stand .035 compressed with the pistons .007 in the hole leaves me with .042 quench I hope to be close to 9:1 with the Diamond pistons I'm using.


My understanding is you do not want a minimum .040 quench (piston to head clearance)



 http://rjcracing.com/product/head-gasket/

[good2win22]

I measured the piston to deck distance on my barn motor and it is .039 to .040.  So from what you're saying, I'm already at the minimum quench without the head gasket with my current piston sitting that low in the cylinder.  I'm getting in way deep for this motor build and it's enjoyable to learn all this stuff.

[larrym]

if your measurements are correct with a stock gasket you would have .099 quench something doesn't sound right. I am far from an expert but I do like to learn, compression height (piston to deck height) plus compressed gasket thickness equals quench.

[good2win22]

Got a call from my friend at the dodge dealership.  Left work early to go see.  He wouldn't let me drive it.  Buyer is the owner of Bush's Chicken

[TexasT]

Cool, I saw a white one out at one of my big customers. I didn't know what it was but I did see the fender badge with 6.4L. Maybe it isn't the same, ill snap some pix next week.

[TexasT]

if your measurements are correct with a stock gasket you would have .099 quench something doesn't sound right. I am far from an expert but I do like to learn, compression height (piston to deck height) plus compressed gasket thickness equals quench.

On a production engine the designer usually shoots for the piston to be in the hole to account for production variations, so the piston doesn't end up out of the hole and causing problems(at least this is what I have read). This could account for performance variations with seemingly identical cars.

[good2win22]

if your measurements are correct with a stock gasket you would have .099 quench something doesn't sound right. I am far from an expert but I do like to learn, compression height (piston to deck height) plus compressed gasket thickness equals quench.

I just ran the numbers for a stock engine with .030 over bore and came out with 8.05. Here's the numbers I used.   If anyone thinks I have the wrong numbers let me know.


Bore 3.83
Stroke 3.4
Head cc 49
Piston cc 23
Head gasket diameter 3.86
Head gasket thickness .060


That seems to be in line with the stock specs of 8 to 1. 


Next question is how thin of a head gasket can you use and still have valve clearance and still have the intake seal?  I realize there are variables, especially if the heads and deck had to be milled for squareness.

[TexasT]

Put some clay on the piston tops and bolt the heads on w/o a gasket. Put the pushrods and rockers in and turn it over with a breaker bar carefully. then pull it back off and measure the thickness of the clay. wont be exact due to the angles involved but it gets you where you know the valves wont hit the pistons.

[larrym]

My understanding is    .040 is close to the minimum. My buddy recently  finished a motor the rods he got measure .005 longer than stock and after the block was square decked he was .005 outside the hole he runs stock felpro gaskets with no issue. The added compression really wakes it up. My goals are to have similar numbers with my pistons inside the hole.

[Steve Wood]

My understanding is    .040 is close to the minimum. My buddy recently  finished a motor the rods he got measure .005 longer than stock and after the block was square decked he was .005 outside the hole he runs stock felpro gaskets with no issue. The added compression really wakes it up. My goals are to have similar numbers with my pistons inside the hole.

If we are talking stock Buick heads, they are open chamber and conventional quench is meaningless for the most part.  I don't remember what the champion aluminum heads look like, but the TA turbo heads have a closed chamber design that allows one to take advantage of quench.

Either way, compression is good-particularly on street driven cars.  I have been running in the vicinity of 9.5-1 with iron heads for more than 15 years.  If you have aluminum heads, it becomes mandatory to replace the heat lost due to the lousy thermal properties of AL when discussing combustion.

I coped this out of the archives of gnttype many years ago...gives you an idea of what it takes to accomplish a given compression ratio

http://www.vortexbuicks-etc.com/compression_ratio_calculations.htm

[good2win22]

Toying around on the barn motor this evening... How much wear on the timing cover where the cam button rides before the cover is junk?  I measured the outside depth of the groove but the wear is convex being less in the center of where the cam button rides.

[Charlief1]

 You can epoxy a thin piece of steel (1/8) over where the wear is after spot facing the area. It will keep the wear down, but you need to tear into the pump housing to see if it's damaged first.